TDM Multi-Channel ECG Circuit for EDO and Power Line Noise Rejection
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Solution Overview
Problem
Existing electrocardiogram (ECG) measurement technologies face challenges in accurately measuring multiple channels due to electrode DC offset (EDO) and power line interference, which affect measurement accuracy and require additional electrodes or increased power consumption.
Innovation Solution
A TDM-based multi-channel ECG measurement apparatus that uses a pre-charged capacitor to eliminate EDO and periodically takes or supplies current to cancel power line interference, allowing for multiple channel measurements with low power consumption and high integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a switched capacitor method is used to suppress power line interference, then power line interference is reduced, but capacitors and controllers occupy large area and cause great power consumption
Solution Approach 1:
The patent implements periodic charge pump operation synchronized with the power line frequency (50/60 Hz) to cancel power line interference. The charge pump is activated in specific time slots during the TDM measurement cycle, periodically injecting or removing charge to counteract the power line interference without continuous operation, thereby reducing power consumption while maintaining effectiveness.
2Object-affected harmful factors
If a continuous charge pump method is used to suppress power line interference, then power line interference is reduced, but several amplifiers are required increasing area and power consumption
Solution Approach 1:
The patent merges the power line interference cancellation function with the existing TDM measurement architecture by sharing the single amplifier across multiple channels through time interleaving. The charge pump is integrated into the same measurement path, eliminating the need for separate amplifiers for interference cancellation and reducing overall device complexity.
Solution Approach 2:
The single amplifier in the TDM architecture serves multiple functions: it measures ECG signals from multiple channels through time-division multiplexing and simultaneously processes the charge pump output for power line interference cancellation. This multi-functional design eliminates the need for dedicated amplifiers for each function.
3Adaptability or versatility
If FDM method is used to implement multi-channel measurement, then multiple channels are achieved, but several local oscillators and amplifiers are required increasing power consumption
Solution Approach 1:
The patent merges multiple channel measurements into a single time-multiplexed measurement path, using one amplifier and one ADC to serve all channels sequentially. This eliminates the need for separate local oscillators and amplifiers required by FDM, significantly reducing power consumption while maintaining multi-channel capability.
Solution Approach 2:
The TDM method periodically switches between different measurement channels in a time-division sequence, allowing a single amplifier and ADC to measure multiple channels over time. This periodic time-multiplexing replaces the simultaneous frequency-division approach, reducing the number of active components and their associated power consumption.
4Use of energy by stationary object
If TDM method is used to implement multi-channel measurement, then multiple channels are achieved with lower power, but a large parallel capacitor reduces impedance
Solution Approach 1:
The patent segments the EDO elimination function into discrete time slots within the TDM cycle, applying it only to the reference channel measurement rather than continuously across all channels. This segmented approach eliminates the need for a large parallel capacitor that would be required for continuous EDO elimination, thereby maintaining high input impedance while still achieving EDO removal.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables accurate multi-channel ECG measurements with efficient EDO elimination and robustness against power line interference, achieving low power consumption and high integration without reducing input impedance.
Implementation Method 1
remove an electrode DC offset (EDO) through a pre-charged capacitor
Implementation Method 2
periodically take a current out or supply a current to cancel power line interference
Data Source
AI summary
The present disclosure relates to a time-division multiplexing (TDM)-based multi-channel electrocardiogram measurement apparatus and method, which remove the influence of power line interference in a way to implement multiple channels by using a TDM method, remove an electrode DC offset (EDO) through a pre-charged capacitor, and periodically take a current out or supply a current. The TDM-based multi-channel electrocardiogram measurement apparatus and method robust against power line interference according to the present disclosure have advantages in that it can measure electrocardiogram by using multiple channels with low power and high integration based on TDM, can perform contactless measurement because an EDO is efficiently eliminated and high impedance is satisfied, and has a characteristic robust against power line interference.